From 86e56f08c897b4c67342180c339b2d898fdb6f04 Mon Sep 17 00:00:00 2001 From: Roger Song Date: Tue, 1 Apr 2025 10:47:13 +0800 Subject: [PATCH 1/5] include notice in release note --- releases/release-7.2.0.md | 2 ++ 1 file changed, 2 insertions(+) diff --git a/releases/release-7.2.0.md b/releases/release-7.2.0.md index e0ffa205f982d..a5fbb9c6257f6 100644 --- a/releases/release-7.2.0.md +++ b/releases/release-7.2.0.md @@ -174,6 +174,8 @@ Quick access: [Quick start](https://docs.pingcap.com/tidb/v7.2/quick-start-with- - When processing update event, TiCDC splits an event into delete and insert events if the primary key or non-null unique index value is modified in the event. For more information, see [documentation](/ticdc/ticdc-split-update-behavior.md#transactions-containing-a-single-update-change). +- The default value of [`tidb_remove_orderby_in_subquery`](/system-variables.md#tidb_remove_orderby_in_subquery-new-in-v610) has been changed from `OFF` to `ON` to avoid unnecessary sorting operations. This change may result in a different order of query results. The ISO/IEC SQL standard does not require query results to follow the ORDER BY sorting of subqueries. To strictly guarantee the final result order, sorting should be explicitly included in the outer query. Applications that rely on subquery sorting can set this variable to `OFF`. Clusters upgraded from older versions will retain the previous behavior by default. + ### System variables | Variable name | Change type | Description | From 17746e5ebd7b224a3172ce57947cc52ce2dfd033 Mon Sep 17 00:00:00 2001 From: Roger Song Date: Thu, 10 Apr 2025 11:19:00 +0800 Subject: [PATCH 2/5] accept suggestions from bot Co-authored-by: gemini-code-assist[bot] <176961590+gemini-code-assist[bot]@users.noreply.github.com> --- releases/release-7.2.0.md | 3 +-- 1 file changed, 1 insertion(+), 2 deletions(-) diff --git a/releases/release-7.2.0.md b/releases/release-7.2.0.md index a5fbb9c6257f6..8911740edd6b8 100644 --- a/releases/release-7.2.0.md +++ b/releases/release-7.2.0.md @@ -173,8 +173,7 @@ Quick access: [Quick start](https://docs.pingcap.com/tidb/v7.2/quick-start-with- ### Behavior changes - When processing update event, TiCDC splits an event into delete and insert events if the primary key or non-null unique index value is modified in the event. For more information, see [documentation](/ticdc/ticdc-split-update-behavior.md#transactions-containing-a-single-update-change). - -- The default value of [`tidb_remove_orderby_in_subquery`](/system-variables.md#tidb_remove_orderby_in_subquery-new-in-v610) has been changed from `OFF` to `ON` to avoid unnecessary sorting operations. This change may result in a different order of query results. The ISO/IEC SQL standard does not require query results to follow the ORDER BY sorting of subqueries. To strictly guarantee the final result order, sorting should be explicitly included in the outer query. Applications that rely on subquery sorting can set this variable to `OFF`. Clusters upgraded from older versions will retain the previous behavior by default. +- The default value of [`tidb_remove_orderby_in_subquery`](/system-variables.md#tidb_remove_orderby_in_subquery-new-in-v610) has been changed from `OFF` to `ON` to avoid unnecessary sorting operations, which improves query performance in many cases. This change may result in a different order of query results. The ISO/IEC SQL standard does not require query results to follow the ORDER BY sorting of subqueries. To strictly guarantee the final result order, sorting should be explicitly included in the outer query. Applications that rely on subquery sorting can set this variable to `OFF`. Clusters upgraded from older versions will retain the previous behavior by default. ### System variables From 40abbde28628ea78ad6d8f5c23e40f6ececad8b1 Mon Sep 17 00:00:00 2001 From: xixirangrang Date: Thu, 10 Apr 2025 18:23:46 +0800 Subject: [PATCH 3/5] Update release-7.2.0.md --- releases/release-7.2.0.md | 3 +-- 1 file changed, 1 insertion(+), 2 deletions(-) diff --git a/releases/release-7.2.0.md b/releases/release-7.2.0.md index 8911740edd6b8..5240f08d9e8d3 100644 --- a/releases/release-7.2.0.md +++ b/releases/release-7.2.0.md @@ -173,7 +173,6 @@ Quick access: [Quick start](https://docs.pingcap.com/tidb/v7.2/quick-start-with- ### Behavior changes - When processing update event, TiCDC splits an event into delete and insert events if the primary key or non-null unique index value is modified in the event. For more information, see [documentation](/ticdc/ticdc-split-update-behavior.md#transactions-containing-a-single-update-change). -- The default value of [`tidb_remove_orderby_in_subquery`](/system-variables.md#tidb_remove_orderby_in_subquery-new-in-v610) has been changed from `OFF` to `ON` to avoid unnecessary sorting operations, which improves query performance in many cases. This change may result in a different order of query results. The ISO/IEC SQL standard does not require query results to follow the ORDER BY sorting of subqueries. To strictly guarantee the final result order, sorting should be explicitly included in the outer query. Applications that rely on subquery sorting can set this variable to `OFF`. Clusters upgraded from older versions will retain the previous behavior by default. ### System variables @@ -181,7 +180,7 @@ Quick access: [Quick start](https://docs.pingcap.com/tidb/v7.2/quick-start-with- |--------|------------------------------|------| | [`last_insert_id`](/system-variables.md#last_insert_id) | Modified | Changes the maximum value from `9223372036854775807` to `18446744073709551615` to be consistent with that of MySQL. | | [`tidb_enable_non_prepared_plan_cache`](/system-variables.md#tidb_enable_non_prepared_plan_cache) | Modified | Changes the default value from `OFF` to `ON` after further tests, meaning that non-prepared execution plan cache is enabled. | -| [`tidb_remove_orderby_in_subquery`](/system-variables.md#tidb_remove_orderby_in_subquery-new-in-v610) | Modified | Changes the default value from `OFF` to `ON` after further tests, meaning that the optimizer removes the `ORDER BY` clause in a subquery. | +| [`tidb_remove_orderby_in_subquery`](/system-variables.md#tidb_remove_orderby_in_subquery-new-in-v610) | Modified | Changes the default value from `OFF` to `ON` after further tests, meaning that the optimizer removes the `ORDER BY` clause in a subquery. This can avoid unnecessary sorting operations, which improves query performance in many cases. This change might result in a different order of query results. The ISO/IEC SQL standard does not require query results to follow the `ORDER BY` sorting of subqueries. To strictly guarantee the final result order, sorting must be explicitly included in the outer query. You can set this variable to `OFF` for applications that rely on subquery sorting. Clusters upgraded from earlier versions retain the previous behavior by default. | | [`tidb_analyze_skip_column_types`](/system-variables.md#tidb_analyze_skip_column_types-new-in-v720) | Newly added | Controls which types of columns are skipped for statistics collection when executing the `ANALYZE` command to collect statistics. The variable is only applicable for [`tidb_analyze_version = 2`](/system-variables.md#tidb_analyze_version-new-in-v510). When using the syntax of `ANALYZE TABLE t COLUMNS c1, ..., cn`, if the type of a specified column is included in `tidb_analyze_skip_column_types`, the statistics of this column will not be collected. | | [`tidb_enable_check_constraint`](/system-variables.md#tidb_enable_check_constraint-new-in-v720) | Newly added | Controls whether to enable `CHECK` constraints. The default value is `OFF`, which means this feature is disabled. | | [`tidb_enable_fast_table_check`](/system-variables.md#tidb_enable_fast_table_check-new-in-v720) | Newly added | Controls whether to use a checksum-based approach to quickly check the consistency of data and indexes in a table. The default value is `ON`, which means this feature is enabled. | From 244cd5a0f7fde4dcc48b52aafe10717a8e019d91 Mon Sep 17 00:00:00 2001 From: houfaxin Date: Fri, 11 Apr 2025 09:07:15 +0800 Subject: [PATCH 4/5] Update release-7.2.0.md --- releases/release-7.2.0.md | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/releases/release-7.2.0.md b/releases/release-7.2.0.md index 5240f08d9e8d3..67234b198f815 100644 --- a/releases/release-7.2.0.md +++ b/releases/release-7.2.0.md @@ -173,6 +173,7 @@ Quick access: [Quick start](https://docs.pingcap.com/tidb/v7.2/quick-start-with- ### Behavior changes - When processing update event, TiCDC splits an event into delete and insert events if the primary key or non-null unique index value is modified in the event. For more information, see [documentation](/ticdc/ticdc-split-update-behavior.md#transactions-containing-a-single-update-change). +- Changes the default value of [`tidb_remove_orderby_in_subquery`](/system-variables.md#tidb_remove_orderby_in_subquery-new-in-v610) from `OFF` to `ON`, meaning that the optimizer removes the `ORDER BY` clause in a subquery. This can avoid unnecessary sorting operations, which improves query performance in many cases. This change might result in a different order of query results. The ISO/IEC SQL standard does not require query results to follow the `ORDER BY` sorting of subqueries. To strictly guarantee the final result order, sorting must be explicitly included in the outer query. You can set this variable to `OFF` for applications that rely on subquery sorting. Clusters upgraded from earlier versions retain the previous behavior by default. ### System variables @@ -180,7 +181,7 @@ Quick access: [Quick start](https://docs.pingcap.com/tidb/v7.2/quick-start-with- |--------|------------------------------|------| | [`last_insert_id`](/system-variables.md#last_insert_id) | Modified | Changes the maximum value from `9223372036854775807` to `18446744073709551615` to be consistent with that of MySQL. | | [`tidb_enable_non_prepared_plan_cache`](/system-variables.md#tidb_enable_non_prepared_plan_cache) | Modified | Changes the default value from `OFF` to `ON` after further tests, meaning that non-prepared execution plan cache is enabled. | -| [`tidb_remove_orderby_in_subquery`](/system-variables.md#tidb_remove_orderby_in_subquery-new-in-v610) | Modified | Changes the default value from `OFF` to `ON` after further tests, meaning that the optimizer removes the `ORDER BY` clause in a subquery. This can avoid unnecessary sorting operations, which improves query performance in many cases. This change might result in a different order of query results. The ISO/IEC SQL standard does not require query results to follow the `ORDER BY` sorting of subqueries. To strictly guarantee the final result order, sorting must be explicitly included in the outer query. You can set this variable to `OFF` for applications that rely on subquery sorting. Clusters upgraded from earlier versions retain the previous behavior by default. | +| [`tidb_remove_orderby_in_subquery`](/system-variables.md#tidb_remove_orderby_in_subquery-new-in-v610) | Modified | Changes the default value from `OFF` to `ON` after further tests, meaning that the optimizer removes the `ORDER BY` clause in a subquery. | | [`tidb_analyze_skip_column_types`](/system-variables.md#tidb_analyze_skip_column_types-new-in-v720) | Newly added | Controls which types of columns are skipped for statistics collection when executing the `ANALYZE` command to collect statistics. The variable is only applicable for [`tidb_analyze_version = 2`](/system-variables.md#tidb_analyze_version-new-in-v510). When using the syntax of `ANALYZE TABLE t COLUMNS c1, ..., cn`, if the type of a specified column is included in `tidb_analyze_skip_column_types`, the statistics of this column will not be collected. | | [`tidb_enable_check_constraint`](/system-variables.md#tidb_enable_check_constraint-new-in-v720) | Newly added | Controls whether to enable `CHECK` constraints. The default value is `OFF`, which means this feature is disabled. | | [`tidb_enable_fast_table_check`](/system-variables.md#tidb_enable_fast_table_check-new-in-v720) | Newly added | Controls whether to use a checksum-based approach to quickly check the consistency of data and indexes in a table. The default value is `ON`, which means this feature is enabled. | From 6d4b7c92a1f4359ad0255afa1954ded0e30550d0 Mon Sep 17 00:00:00 2001 From: houfaxin Date: Fri, 11 Apr 2025 09:14:24 +0800 Subject: [PATCH 5/5] Update release-7.2.0.md --- releases/release-7.2.0.md | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/releases/release-7.2.0.md b/releases/release-7.2.0.md index 67234b198f815..ebe5da4915c63 100644 --- a/releases/release-7.2.0.md +++ b/releases/release-7.2.0.md @@ -173,7 +173,7 @@ Quick access: [Quick start](https://docs.pingcap.com/tidb/v7.2/quick-start-with- ### Behavior changes - When processing update event, TiCDC splits an event into delete and insert events if the primary key or non-null unique index value is modified in the event. For more information, see [documentation](/ticdc/ticdc-split-update-behavior.md#transactions-containing-a-single-update-change). -- Changes the default value of [`tidb_remove_orderby_in_subquery`](/system-variables.md#tidb_remove_orderby_in_subquery-new-in-v610) from `OFF` to `ON`, meaning that the optimizer removes the `ORDER BY` clause in a subquery. This can avoid unnecessary sorting operations, which improves query performance in many cases. This change might result in a different order of query results. The ISO/IEC SQL standard does not require query results to follow the `ORDER BY` sorting of subqueries. To strictly guarantee the final result order, sorting must be explicitly included in the outer query. You can set this variable to `OFF` for applications that rely on subquery sorting. Clusters upgraded from earlier versions retain the previous behavior by default. +- Changes the default value of [`tidb_remove_orderby_in_subquery`](/system-variables.md#tidb_remove_orderby_in_subquery-new-in-v610) from `OFF` to `ON`, meaning that the optimizer removes the `ORDER BY` clause in a subquery. This can avoid unnecessary sorting operations, which improves query performance in many cases. This change might result in a different order of query results. The ISO/IEC SQL standard does not require query results to follow the `ORDER BY` sorting of subqueries. To strictly guarantee the final result order, sorting must be explicitly included in the outer query. If your applications rely on subquery sorting, you can set this variable to `OFF`. Clusters upgraded from earlier versions retain the previous behavior by default. ### System variables